通用分页查询

项目思路：

1.页面：

　　包括：结果集，分页控件

2.Servlet

3.查询Dao:

　　(1) 查询总记录数

　　(2) 查询每页数据

4.通用分页Bean

项目源码：

AuthorDao.java:

package com.dao;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.bean.Author;
import com.db.DB;
import com.mysql.jdbc.Connection;
import com.mysql.jdbc.PreparedStatement;

public class AuthorDao {
    
    //检验用户名或密码是否正确
    public Author CheckLogin(String username,String password) {
        Author author=null;
        DB db=new DB();
        //获取数据库连接对象
        Connection con=(Connection) db.getCon();
        
        //定义sql语句
        String sql="select * from author where username= ? and password= ?";
        
        try {
            PreparedStatement ps=(PreparedStatement) con.prepareStatement(sql);
            //设置用户名和密码和密码作为参数放到sql
            ps.setString(1,username);
            ps.setString(2, password);
            
            ResultSet rs=ps.executeQuery();
            
            //用户名和密码正确，得到用户数据，进行打包
            if(rs.next()) {
                author=new Author();
                author.setId(rs.getInt(1));
                author.setUsername(rs.getString(2));
                author.setPassword(rs.getString(3));
                author.setEmail(rs.getString(4));
                author.setAddress(rs.getString(5));
                author.setPhone(rs.getString(6));
                
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
        return author;
    }
    
    
    //查询所有用户信息
    public List<Author> selectallauthor(){
        List<Author> authorlist=new ArrayList<Author>();
        DB db=new DB();
        
        //获取数据库连接对象
        Connection con=(Connection) db.getCon();
        String sql="select * from author";
        
        try {
            
            PreparedStatement ps=(PreparedStatement) con.prepareStatement(sql);
            
            ResultSet rs=ps.executeQuery();
            
            //循环遍历获取用户信息
            while(rs.next()) {
                Author author=new Author();
                author.setId(rs.getInt(1));
                author.setUsername(rs.getString(2));
                author.setPassword(rs.getString(3));
                author.setEmail(rs.getString(4));
                author.setAddress(rs.getString(5));
                author.setPhone(rs.getString(6));
                
                authorlist.add(author);
                //System.out.println("存放成功");
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
        
        return authorlist;
    }
    
    //查询用户表总记录数（分页查询）
    public int selectallauctorcount() {
        DB db=new DB();
        Connection con=(Connection) db.getCon();
        String sql="select count(*) from author";
        
        try {
            PreparedStatement ps=(PreparedStatement) con.prepareStatement(sql);
            ResultSet rs=ps.executeQuery();
            
            if(rs.next()) {
                return rs.getInt(1);
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return 0;
    }

    /*
     * 分页查询用户数据类型
     * padeIndex数据起始索引
     * padeSize每页显示的数据条数
     */
    public List<Author> sellectallauthorPage(int pageIndex,int pageSize){
        List<Author> list=new ArrayList<Author>();
        Author author=new Author();
        DB db=new DB();
        Connection con=(Connection) db.getCon();
        String sql="select * from author limit ?,?";
        try {
            PreparedStatement ps=(PreparedStatement) con.prepareStatement(sql);
            ps.setObject(1,pageIndex);
            ps.setObject(2, pageSize);
            ResultSet rs=ps.executeQuery();//获取结果集
            
            //遍历结果集获取用户的列表信息
            while(rs.next()) {
                author=new Author();
                author.setId(rs.getInt(1));
                author.setUsername(rs.getString(2));
                author.setPassword(rs.getString(3));
                author.setEmail(rs.getString(4));
                author.setAddress(rs.getString(5));
                author.setPhone(rs.getString(6));
                
                list.add(author);
                
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return list;
    }
    
    //新增用户信息
    public void add(Author author) {
        
        DB db=new DB();
        Connection con=(Connection) db.getCon();
        
        String sql="insert into author values(id,?,?,?,?,?)";
        try {
            PreparedStatement ps=(PreparedStatement) con.prepareStatement(sql);

            ps.setObject(1,author.getUsername());
            ps.setObject(2,author.getPassword());
            ps.setObject(3,author.getEmail());
            ps.setObject(4,author.getAddress());
            ps.setObject(5, author.getPhone());
            
            ps.execute();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
    //删除用户消息
    public void delete(int id) {
        DB db=new DB();
        Connection con=(Connection) db.getCon();
        
        String sql="delete from author where id=?";
        
        try {
            PreparedStatement ps=(PreparedStatement)con.prepareStatement(sql);
            ps.setObject(1,id);
            
            ps.execute();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
}
AuthorDao

AuthorListPageServlet.java:

package com.servlet;

import java.io.IOException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.bean.Author;
import com.bean.PageBean;
import com.dao.AuthorDao;

/**
 * Servlet implementation class AuthorListPageServlet
 */
@WebServlet("/AuthorListPageServlet")
public class AuthorListPageServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public AuthorListPageServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        request.setCharacterEncoding("utf-8");
        AuthorDao dao=new AuthorDao();
        int pageSize=2;
        String strPage=request.getParameter("currentPage");//接受页面传入的页码
        int record=dao.selectallauctorcount();//总记录数
        int currentPage=1;//默认当前页为第一页
        if(strPage!=null) {
            currentPage=Integer.parseInt(strPage);//当前页码
        }
        PageBean<Author> pb=new PageBean<Author>(currentPage,pageSize,record);       
        List<Author> list=dao.sellectallauthorPage(pb.getPageIndex(),pageSize);//查询某一页的结果集
        pb.setList(list);
        
        request.setAttribute("pageBean", pb);
        request.getRequestDispatcher("userlistpage.jsp").forward(request, response);
    
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}
AuthorListPageServlet

PageBean.java:

package com.bean;

import java.util.List;
/*
 * java中的泛型类和泛型集合
 * 通过使用泛型将工具变成通用的
 */

public class PageBean<T> {
    

    private int currentPage;//当前页码
    private int pageIndex;//数据起始索引
    private int pageSize;//每页条数
    private int record;//总记录数
    private int totalPage;//总页数
    
    private List<T> list;//每页显示的结果集
    
    /*
     * 构造函数初始化pageIndex和totalPage
     */
    public PageBean(int currentPage,int pageSize,int record) {
        this.currentPage=currentPage;
        this.pageSize=pageSize;
        this.record=record;
        
        //总页数
        if(record%pageSize==0) {
            //整数，没有多余的页
            this.totalPage=record/pageSize;    
        }else {
            //有多余的数据再增加一页
            this.totalPage=record/pageSize+1;
        }
        
        //数据起始索引
        if(currentPage<1) {
            this.currentPage=1;
        }else if(currentPage>this.totalPage) {
            this.currentPage=this.totalPage;
        }
        this.pageIndex=(this.currentPage-1)*this.pageSize;
        
    }
    
    
    public PageBean(int currentPage, int pageIndex, int pageSize, int record, int totalPage, List<T> list) {
        super();
        this.currentPage = currentPage;
        this.pageIndex = pageIndex;
        this.pageSize = pageSize;
        this.record = record;
        this.totalPage = totalPage;
        this.list = list;
    }
    public int getCurrentPage() {
        return currentPage;
    }
    public void setCurrentPage(int currentPage) {
        this.currentPage = currentPage;
    }
    public int getPageIndex() {
        return pageIndex;
    }
    public void setPageIndex(int pageIndex) {
        this.pageIndex = pageIndex;
    }
    public int getPageSize() {
        return pageSize;
    }
    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }
    public int getRecord() {
        return record;
    }
    public void setRecord(int record) {
        this.record = record;
    }
    public int getTotalPage() {
        return totalPage;
    }
    public void setTotalPage(int totalPage) {
        this.totalPage = totalPage;
    }
    public List<T> getList() {
        return list;
    }
    public void setList(List<T> list) {
        this.list = list;
    }
    
    

}
PageBean

userlistpage.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@page import="com.bean.PageBean" %>
<%@page import="com.servlet.AuthorListPageServlet" %>
<%@page import="com.dao.AuthorDao" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>显示用户详细信息</title>
</head>
<body>

<table border="1">
    <tr>
        <td>用户名</td>
        <td>邮箱</td>
        <td>地址</td>
        <td>电话</td>        
        <td>操作</td>
    </tr>
     <c:forEach items="${pageBean.list}" var="author">
 
     <tr>
         <td>${author.username }</td>
         <td>${author.email }</td>
         <td>${author.address }</td>
         <td>${author.phone }</td>
         <td><a href="AuthorServlet?op=delete&id=${author.id }">删除</a></td>
     </tr>
 </c:forEach>
</table>
<c:if test="${pageBean.record>0 }">
<div > 
    <a href="AuthorListPageServlet?currentPage=1">首页</a>
    <a href="AuthorListPageServlet?currentPage=${pageBean.currentPage-1 }">上一页</a>
    <a href="AuthorListPageServlet?currentPage=${pageBean.currentPage+1 }">下一页</a>
    <a href="AuthorListPageServlet?currentPage=${pageBean.totalPage }">尾页</a>
</div>
</c:if>
</body>
</html>
userlistpage

项目运行截图：

 遇到的问题：

1.编译失败，没有在AuthorListPageServlet.java:中使用utf-8

解决时间：1分钟

2.显示结果为空

原因：自己的命名混淆，currentPage传值的时候，名字用错

解决时间：6分钟

3.sql语句：中分页查询数据集的sql语句写错 selsect * from author limit ?,?;中忘记关键字limit

解决时间：1分钟

注意项：

1.在AuthorListPageServlet.java:中进行数据封装和传值的时候，应该将PageBean的泛型类进行封装，并闯到前端页面，而不是list容器

2，在算当前页面需要显示数据集的时候，current需要与total进行对比，若超出范围则相对应的显示首页和尾页

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原文地址：https://www.cnblogs.com/hhjing/p/12492364.html